The present invention relates to a key top for a push button switch for use with an input device for a car stereo, car radio or the like, and more particularly to an illuminated key top having an indicating portion adapted to be illuminated.
A known illuminated key top having an indicating portion for indicating letters, symbols, etc. is manufactured by various methods.
For example, the key top is formed by a so-called bicolor molding method wherein an indicator member having the indicating portion is molded, and an outer member is then molded to cover the outer surface of the indicator member except a top surface of the indicating portion to be exposed.
FIG. 6 is a perspective view of the indicator member 1 to be formed by the bicolor molding method, and FIG. 7 is a perspective view of the key top 7 formed by using the indicator member 1 shown in FIG. 6 wherein the indicating portion 2 is illuminated.
Referring to FIG. 6, the indicator member 1 is molded from a transparent or translucent synthetic resin in such a manner as to integrally form a projection 2 as the indicating portion on the top surface of the indicator member 1. Then, as shown in FIG. 7, an outer member 6 is molded from an opaque synthetic resin so as to cover the outer surface of the indicator member 1 except a top surface of the indicating portion 1 to be exposed. Thus, the key top 7 is formed.
In the case that a closed portion 3 is so defined as to be surrounded by the indicating portion 2 as in the numerals "0" and "4", a horizontal groove 4 is formed by inserting a movable slide pin (not shown) for molding the indicator member 1 and then removing the slide pin after molding. Thus, the groove 4 is formed just under the closed portion 3. Then, the synthetic resin for the outer member 6 can fill the groove 4 and the closed portion 3 when molding the outer member 6.
Another method for forming the key top by a laser beam machining process is shown in FIGS. 8A to 8D. Referring first to FIG. 8A, the indicator member 1 is molded from a transparent or translucent synthetic resin. Then, as shown in FIG. 8B, a light transmitting colored coating 8 having a white color, for example, is applied onto an entire outer surface of the indicator member 1. Then, as shown in FIG. 8C, a light shielding colored coating 9 having a black color, for example, is deposited with a desired film thickness onto an entire outer surface of the light transmitting colored coating 8 by painting, sputtering or vapor deposition.
Furthermore, as shown in FIG. 8D, a laser beam 10 irradiates a top surface of the light shielding coating 9 in such a manner as to remove a part of the light shielding coating 9 which corresponds to the indicating portion 2. Thus, the light transmitting colored coating 8 is partially exposed at the indicating portion 2. Finally, a transparent hard coat (not shown) which acts as a protection layer is formed on the entire outer surface of the key top 7 by painting, sputtering or vapor deposition.
When the above-mentioned key top is formed by the bicolor molding method as shown in FIGS. 6 and 7, the synthetic resin for the outer member 6 having a light transmittance less than that of the indicating portion 2 fills the groove 4 under the indicating portion 2. Therefore, when the indicating portion 2 is illuminated from the inside of the key top 7, a portion 5 of the indicating portion 2 which is above the groove 4 filled with the opaque synthetic resin is shaded to cause nonuniformity illumination of the indicating portion 2. Furthermore, because the slide pin is used, the molded structure is complicated which increase the manufacturing cost.
On the other hand, in the key top to be formed by the laser beam machining as shown in FIGS. 8A to 8D, a laser device is used, and means for effecting painting, sputtering or vapor deposition are also used, thus increasing the manufacturing cost. Further, if the indicating portion 2 consists of plural letters or symbols, it is difficult to form the letters or symbols in different colors.